Fluorine doping a soot preform

Abstract

The invention includes a method of incorporating fluorine into a preform that may be used to produce an optical article. A method that may be used to practice the invention includes a method of making an optical fiber preform. The method includes reacting a fluorine containing precursor in a flame of a combustion burner without forming a soot, thereby forming a fluorine doping atmosphere. A further method that may be practiced to practice the invention includes the step reacting at least a fluorine containing precursor in a flame of a combustion burner, wherein the precursors reacted in the flame are substantially devoid of the element of silicon, thereby forming a fluorine containing atmosphere for the doping of a soot preform. An additional method that may be used to practice the invention includes the step of reacting at least one precursor in the flame of a combustion burner, wherein said precursors comprise at least one fluorine containing compound and the precursors are substantially free of any silicon containing compound, and the additional step of directing a reaction product of said reacting step toward a soot preform.

What is claimed is:  
     
       1. A method of making an optical fiber preform comprising: 
       forming a glass soot in a flame of a combustion burner;  
       depositing the soot onto a stalling member to form an optical fiber soot preform;  
       reacting a fluorine containing precursor in said flame without forming a soot, thereby forming a fluorine doping atmosphere;  
       exposing the soot preform to said fluorine doping atmosphere so as to dope the soot preform with flourine.  
     
     
       2. The method according to  claim 1  wherein said combustion burner comprises an array of burners, wherein said array has a length substantially the same as the length of said preform. 
     
     
       3. The method according to  claim 1  wherein a reaction product of said reacting comprises hydrogen fluoride. 
     
     
       4. The method according to  claim 1  wherein a fuel of the flame comprises a hydrogen containing compound. 
     
     
       5. The method according to  claim 1  wherein a ratio of fluorine in the precursor to hydrogen in a fuel of the flame comprises about 1:1. 
     
     
       6. The method according to  claim 1  wherein said soot comprises at least one of the following types of soot: undoped soot, fluorine-doped soot, germanium-doped soot, phosphorus-doped soot, aluminum doped soot, antimony-doped soot, tantalum-doped soot, and combinations thereof. 
     
     
       7. The method according to  claim 1  wherein a fuel for the flame comprises a substantially hydrogen free compound. 
     
     
       8. The method according to  claim 1  wherein a reaction temperature of said reacting comprises at least about 500° C. and less than about 1200° C. 
     
     
       9. The method according to  claim 1  further comprising preheating said soot preform to a substantially uniform radial temperature below the sintering temperature of said soot preform. 
     
     
       10. The method according to  claim 1  wherein a reaction temperature of said reacting comprises a temperature below the sintering temperature of the soot preform. 
     
     
       11. The method according to  claim 1  further comprising maintaining a partial pressure of fluorine doping atmosphere at a substantially constant value. 
     
     
       12. The method according to  claim 1  further comprising maintaining a temperature of said soot preform at a substantially uniform radial temperature. 
     
     
       13. The method according to  claim 1  wherein a ratio of fluorine in the precursor to hydrogen in a fuel of the flame comprises about 2:1 or greater. 
     
     
       14. The method according to  claim 1  further comprising aligning said burner adjacent said soot preform in a radial direction. 
     
     
       15. The method according to  claim 1  further comprising aligning said burner axially to said soot preform. 
     
     
       16. The method according to  claim 1  wherein a product of said reacting comprises at least about 0.1% by volume at least one component of the group consisting of COF, COF 3 , COF 2 , S 2 F 2 , SOF 2 , and combinations thereof. 
     
     
       17. The method according to  claim 1  further comprising applying heat to said soot preform by a source other than the burner during said reacting step. 
     
     
       18. The method according to  claim 17  wherein said source comprises at least one heat lamp. 
     
     
       19. The method according to  claim 1  further comprising partially enclosing said soot preform in an enclosure wherein a distance between the enclosure and the preform comprises no more than about 12 cm. 
     
     
       20. The method according to  claim 1  further comprising introducing a chlorine containing precursor into said flame. 
     
     
       21. The method according to  claim 1  wherein a product of said reacting comprises at least about 0.1% by volume at least one component of the group consisting of COF 2 , S 2 F 2 , SOF 2 , and combinations thereof. 
     
     
       22. A method of doping an optical fiber preform comprising: 
       reacting at least a fluorine containing precursor in a flame of a combustion burner, wherein the precursors reacted in the flame are substantially devoid of a silicon containing compound that may be reacted in said flame to form a soot particle, thereby forming a fluorine containing atmosphere for the doping of a soot preform.  
     
     
       23. The method according to  claim 22  wherein said combustion burner comprises an array of burners, wherein said array has length substantially the same as the length of said preform. 
     
     
       24. The method according to  claim 22  wherein a reaction product of said reacting comprises hydrogen fluoride. 
     
     
       25. The method according to  claim 22  wherein a fuel of the flame comprises a hydrogen containing compound. 
     
     
       26. The method according to  claim 22  further comprising preheating said soot preform to a substantially uniform radial temperature below the sintering temperature of a soot preform. 
     
     
       27. The method according to  claim 22  wherein a reaction temperature of said reacting comprises a temperature below the sintering temperature of a soot preform. 
     
     
       28. The method according to  claim 22  further comprising maintaining a partial pressure of fluorine in an atmosphere created from said reacting at a substantially constant value. 
     
     
       29. A method of making an optical fiber comprising: 
       forming a glass soot in a flame of a combustion burner;  
       depositing the soot onto a starting member to form an optical fiber soot preform;  
       reacting at least one precursor in the flame of said combustion burner, wherein said precursors comprise at least one fluorine containing compound and said precursors are substantially free of any silicon containing compound;  
       directing a reaction product of said reacting step toward said soot preform so as to dope the soot preform with fluorine;  
       drawing the sintered preform to form an optical fiber.  
     
     
       30. The method according to  claim 1  wherein a ratio of fluorine in the precursor to hydrogen in a fuel of the flame comprises about 1:1. 
     
     
       31. The method according to  claim 1  wherein a product of said reacting comprises at least about 0.1% by volume at least one compound containing fluorine and substantially devoid of hydrogen. 
     
     
       32. The method according to  claim 1  wherein the starting member is a core cane. 
     
     
       33. The method according to  claim 29  wherein the starting member is a core cane.